Pigmented rubber hydrohalides



Patented July 1, 1941 PIGMENTED RUBBER HYDROHALIDES James B. Holden,Akron, Ohio, assignor to Wingfoot Corporation, Wilmington, Del., acorporation of Delaware No Drawing.

Original application February 8,

1936, Serial No. 62,992. Divided and this application July 13, 1938,Serial No. 219,032

1 Claim.

This invention relates to the hydrohalide derivatives of rubber. Moreparticularly, it relates to the compounding of such materials withpigments to yield very desirable products.

Hydrohalide derivatives of rubber are well known. It is also known thatthis type of material can be utilized to form films of excellentmoisture proofness and other desirable physical characteristics. Rubberhydrochloride may be taken as representative.

One of the outstanding diificulties with films made of rubberhydrochloride is their tendency to deteriorate through ageing. Variousmethods have been proposed for retarding this deterioration.

It has now been discovered that this deterioration may be greatlyretarded by incorporating into the rubber hydrochloride certainpigments. Besides imparting longer life to the film, certain of thesepigments produce other outstanding effects of great usefulness andvalue.

' The pigments are preferably added to the rubber hydrochloride cementprior to the spreading and formation of the film.

Any of the known methods of securing proper dispersion may be employed.It has been found, for example, that dry aluminum powder may be addeddirectly to a seven percent solution of rubber hydrochloride in benzeneand a satisfactory dispersion obtained by simple mixing, as by rollingor the use of a high speed stirrer. This does, however, tend to entrapair in the cement and produce pinholes in the subsequently formed film.This pinhole formation can be largely eliminated by allowing the cementto stand before spreading so that the air can separate. Perhaps evenbetter results are obtained by using the aluminum in the paste form inwhich it is obtainable wetted with a gasoline fraction.

Of course, the finer particle pigments disperse with more difiiculty andit may become advisable to grind the pigment, in a ball mill orotherwise, with the rubber hydrochloride cement or with the plasticizerwhich is to be incorporated in the cement.

One method which has been found very satisfactory with fine particlepigments, such as carbon black, has been to mill the pigment into aresin such as the chlorostannlc acid reaction product of rubber. Thispigmented resin is then dissolved in a small amount of benzene, withexcellent pigment dispersion and this dispersion is added to the rubberhydrochloride cement.

Any other method of adding the pigment may be employed if desired.

Following are the formulae of a number of representative pigmentedrubber hydrochloride films which demonstrate the invention, Sample Abeing an unpigmented control. Proportions are parts by weight. The termPliolite is used to designate the chlorostannic acid reaction product ofrubber.

Formula parts rubber hydrochloride. parts butyl stearate. parthexamethylene tetmmine. .00 parts rubber hydrochloride. 0.00 parts butylstearate. .20 parts Pliolite.

00 parts titanium oxide. part hexamethylene tetramine. 00.00 partsrubber hydrochloride. 10.00 parts butyl stearate. 16.50 parts Pliolite.5.00 parts para red toner. 0.75 part hexamethylene tetramine. 00.00parts rubber hydrochloride. 0.00 parts butyl stearate. 16.00 partsPliolite. 4.60 parts chrome green. 3.30 parts lead ehromate. 0.75 parthexametbylene tetramine. 00.00 parts rubber hydrochloride.

.00 parts butyl stearate. .00 parts Pliolite.

0 parts Prussian blue. 0 parts titanium dioxide. part hexamethylenetetramine. .00 parts rubber hydrochloride. .00 parts butyl stearate.

parts Pliolite. parts red iron oxide. parts carbon black. parthexamethylene tetraniine. .00 parts rubber hydrochloride. .00 partsbutyl stearate.

parts Pliolite. parts carbon black. part hexamethylene tetremine. .00parts rubber hydrochloride. .00 parts butyl stearate.

parts aliuninum powder. part hexamethylene tetramine.

Films of these compositions and 0.001 inch thick were made and exposedto sunlight behind window glass on a roof at an angle of 45 degreesfacing south. The following table shows the times required for thevarious films to become brittle.

These data show the marked difierences in elfect of different pigments.Sample A, a clear, unpigmented film, is the control. Film B is muchinferior to the control, C and D are somewhat inferior, E is the aboutthe same, and F, G and H are very much superior. Thus, various pigmentsaffect the ageing qualities of the film not only in degree but actuallyin kind, i. e., to advantage or disadvantage. It is shown that somepigments very greatly increase the resistance to ageing of the film.

Of course, this method of adding to the useful life of the film cannotbe employed when a clear, transparent product is desired. However, manyapplications arise in which opacity and color are no detriment or evenan advantage.

According to the data above given, carbon black, red iron oxide, andaluminum are outstanding in anti-ageing action. Prussian blue also seemsto have some beneficial efitect. In sample E, the Prussian blue verysuccessfully neutralizes the detrimental effect of titanium dioxidewhich is demonstrated by Sample B.

Thus, it is intendedthat the invention shall include the use of pigmentsto improve the ageing of the film over that of the uncompounded materialor to neutralize the ill effects of other compounding ingredients.

Also, it is not intended that the invention shall be limited to the useof only those materials which are shown by the included data to bebeneficial. There are many other pigments and compoundings which areoperable and the invention includes all of these.

It is not known for certain what mechanism is involved in the protectiveaction of these pigments. It appears that they may function in two ways.It is known that ultra-violet light causes rubber hydrochloride todeteriorate. It is also known that aluminum reflects ultra-violet lightvery efiiciently. It is also, of course, well known that black and otherdark bodies are very efiicient absorbents of energy. It thus seemslogical to suppose that'these pigments function either by reflecting theultra-violet energy or by absorbing it and converting it to a lessdetrimental form such as the longer wave-length heat energy. Any pigmentoperating in either of these manners would be operable.

The product obtained by incorporating finely divided aluminum intorubber hydrochloride possesses other very desirable and noteworthycharacteristics in addition to its improved ageing qualities. In thefirst place it possesses a very good metallic lustre, which suggests itsuse, on an appearance basis, as an alternative for metallie aluminumfoil. In several respects it is very much superior to metallic aluminumfoil. The resistance to the diffusion of water vapor, carbon dioxide,and other gases is higher for rubber hydrochloride containing powderedaluminum than for the unpigmented film. This value is much superior tothat obtained with metallic aluminum foil. This last perhaps surprisingfact is explained by the fact that aluminum, in being rolled down tothin foil, tends to develop minute pinholes which render it lessimpervious to gas diffusion than might be supposed. My new product isalso much stronger than aluminum foil, particularly in its resistance totearing and creasing. Also, it retains the characteristics ofunpigmented rubber hydrochloride of being heat sealable at moderatetemperature, as, for example, at 230 F.

A wide variety of appearance effects are obtainable in this film ofmetallic appearance, as by the addition of dyes, the blending with otherpigments, and theuse of colored aluminum pigments.

Rubber hydrochloride film containing finely divided aluminum is,therefore, one of the preferred forms of the invention. However, manyother compoundings are also included, as heretofore explained.

Thus, although only the preferred forms of the invention have beendescribed in detail, it will be obvious to those skilled in the art thatmany modifications may be made therein without departing from the spiritof the invention or the scope of the appended claim, in which it isintended to cover by suitable expression all features of patentablenovelty inherent in the invention.

This application is a division of my prior application Serial No.62,992, filed February 8, 1936.

What I claim is:

A plastic composition comprising as an essential ingredient a rubberhydrochloride intimately admixed with a minor proportion of leadchromate.

JAMES B. HOLDEN.

